1. Field of the Invention
This invention relates to polyisobutylcarboxylic acid amide compositions useful as detergent additives in hydrocarbon fuels and oils.
2. Description of the Prior Art
Detergent-dispersant additives for hydrocarbon fuels and oils share the common characteristics of a relatively long-chain hydrocarbon oleophilic group having one or more highly polar groups thereon. Such additives may be acids, amides, imides and the like.
Currently employed commercial detergent-dispersants include N-substituted long-chain alkenyl succinimide and related products usually prepared by the condensation of a polyamine with the reaction product of a long-chain olefin and maleic anhydride. Generally, the long-chain alkenyl group is a polyisobutenyl group derived from polyisobutylene having a molecular weight of about 800 to 1500.
While the N-substituted polyisobutenylsuccinimide dispersants are effective, particularly at low temperatures, they have not been entirely satisfactory because of their susceptibility to oxidation (because of the unsaturated polyisobutenyl group) and their tendency towards hydrolysis (of the imide group). Such oxidation and hydrolysis will impair their effectiveness as detergent-dispersant additives for hydrocarbon fuels and lubricating oils.
Potential sources of detergent-dispersants having amide functionally include polyisobutylenes derived from isobutylenes which have oxidizable olefinic linkages at or near terminal carbon atoms. U.S. Pat. No. 3,647,691 discloses additives for lubricating oils which are condensation products of certain amines with long-chain ketones or aldehydes prepared by the reaction of polyolefins (including polyisobutylenes) with ozone. British patent specification No. 1,027,410 discloses lubricant additives which are condensation products of certain amines with the nitric acid oxidation product of polyisobutylenes.
U.S. Pat. No. 3,715,313 discloses oxidation of certain polyisobutylenes with ozone followed by hydrogen peroxide to provide polyisobutylcarboxylic acids in about 30% yield. U.S. Pat. No. 3,219,666 concerns polyisobutenylsuccinic acid derivatives as well as nontertiary polyisobutylcarboxylic acids. U.S. Pat. No. 3,897,224 concerns amides made from acids which have significant unsaturation and a significant number of nontertiary carbon atoms. U.S. Pat. No. 3,931,024 concerns amine additives prepared from high molecular weight oxygenated polyolefins which are made by heating the polymer in the presence of air. British patent specification No. 1,172,818 concerns condensing a polyamine with a ketone which is made by ozonizing a polyolefin and treating the ozonized polyolefin with hydrogen.
Several weaknesses, alone or in combination, characterize each of the various products of the art. The weaknesses include poor oxidative stability, and too-low acid contents. One skilled in the art will appreciate the difficulty of separating polyisobutylcarboxylic acids from a reaction mixture of such acids and a neutral by-product in an effort to concentrate the acid portion (more desirable) of the reaction product. Thus, one skilled in the art will appreciate the desirability of obtaining oxidation products of high acid content without the need to further concentrate the acid.